The invention is based on an electromechanical brake for motor vehicles.
In brakes of this kind, an automatic release of the friction lining must be assured in the event of a failure of the electric drive motor during a braking maneuver. In a disc brake of this type, which is known from WO96/03301, a push rod is therefore disposed between the spindle and the plate-shaped coupling member fastened to the brake lining in order to minimize friction-induced efficiency losses inside a selflocking-free planetary roller screw drive that contains the spindle. Since the brake lining in the caliper has a play that is necessary for the proper functioning of the disc brake, when the brake lining presses against the brake disc, a displacement of the coupling element attached to the brake lining takes place, both in the disc circumference direction and lateral to this, with the result that the push rod transmits lateral forces onto the spindle. The desired lack of friction of the planetary roller screw drive is therefore not achieved so that an automatic release of the brake lining is not always assured in the event of a malfunction.
In an electromechanical brake of this generic type for motor vehicles according to DE 196 07 295 C1, a layer-shaped or disc-shaped slide bearing is disposed as a coupling member between a spindle rod of a planetary roller threaded spindle and a brake lining, and this coupling member is intended to achieve a lateral force de-coupling between the spindle rod and the brake lining. As a result, a sliding mobility lateral to the longitudinal axis of the spindle is provided between the spindle rod and the slide bearing. Due to the relatively large area of contact between the spindle rod and the slide bearing, there is no automatic restoring of the spindle rod in the event of a drive motor failure.
U.S. Pat. No. 5,219,048 has disclosed an electromechanical brake in which brake linings with a ball/ramp mechanism can be moved in relation to a rotating friction element. The brake linings are connected to a caliper or a wear-balancing device of the brake by means of retaining brackets.
The brake according to the invention, has an advantage over the prior art that at the beginning of the pressing of the brake lining against the friction element, the brake lining can be displaced in relation to the coupling member while the latter maintains its orientation relative to the spindle. As a result, lateral forces on the spindle are largely prevented so that its automatic restoring is assured in the event of a drive motor failure. This automatic restoring is encouraged by the friction-reducing bearing embodiment between the spindle and the coupling member. Moreover, the brake is shorter since the spindle engages the coupling member without a push rod.
Advantageous improvements and updates of the brake possible by means of the measures taken hereinafter.
The measures taken also serve to achieve the embodiment of the coupling member and spindle as well as the friction reduction.
The improvement of the brake set forth achieves an automatic restoring of the brake lining relative to the coupling member at the end of braking.
The measures set forth has the advantage that when the brake is released, play is prevented between the brake lining, the coupling member, and the spindle.